City By The Spire
from the back cover:
Ptolus is here! this high quality book offers almost 700 pages of source and adventure material from one of the industry's greatest designers, A fantasy city built above extensive dungeons beside the spire of an ancient foe, Ptolus is a self-contained campaign --- or insert it into your home setting, if you prefer. Its unique design makes it the most DM-friendly book on your shelf, And the CD-Rom inside contains 400+ pages of bonus material, including "The Night of Dissolution", an all-new 96-page adventure, Ptolus was created by one of the architects of 3rd Edition for the gaming professionals in his group.